In the case of gas turbines with fuel oil operation, the fuel oil or the liquid fuel after operation must be removed from the burners and from the supply pipelines which are connected to them in order to prevent coking of the fuel oil on their hot surfaces. The coking would block lines and burners and therefore make them unusable.
A method is known from EP 0 939 220 A1, in which the burners and supply lines of gas turbines are flushed in order to therefore remove the fuel oil from the lines or from the burner. The known emptying of the fuel oil lines takes place in two steps: first of all the burners are flushed. For this purpose, water is pushed via a water line of an NOx-water supply (which for fuel oil/water-emulsion operation is available anyway) via a T-piece which is close to the burner into the fuel oil line rearwards in the direction of the fuel oil supply (fuel oil-water injection package), from where it is transported via open valves of a multifunction valve into an emptying facility. In the case of the flushing method of this type and the associated fuel system, the retention of residues in the fuel oil line may occur in the case of specific operating conditions.
A flushing system for the oil fuel line of a gas turbine burner is also known from US 2002/0026784. It is provided there that air or water for flushing can be fed to the fuel line via separate lines. The flushing can in that case take place successively or else at the same time. An analogous system for gas fuel lines is also known from U.S. Pat. No. 5,784,875.
In addition, US 2007/0289308 A1 discloses a fuel feed line in which the fuel that is in it can be sucked back out of the fuel line with the aid of an inversely driven fuel distributor. This fuel is subsequently returned into a collecting tank. Furthermore, it is known from U.S. Pat. No. 4,041,695 to combine a number of valves in a common valve block.